the medium bomber contract. No YB-25 was available for prototype service tests. In September 1939, the Air Corps ordered the NA-62 into production as the B-25, along with the other new Air Corps medium bomber, the Martin B-26 Marauder "off the drawing board". Variants NA-40 A twin-engined, five-seat bomber to meet 1938 USAAF requirement for an attack bomber, it was powered by two Pratt & Whitney R-1830-56C3G radials. Wingspan was 66 ft (20.12 m), and length 48 ft 3 in (14.71 m). First flown on 29 January 1939, it proved to be underpowered and unstable. NA-40B The NA-40B (also known as the NA-40-2) was a modification of the NA-40 prototype with two Wright R-2600-A71-3 radials and numerous minor changes. It first flew in revised form on 1 March 1939, but crashed on 11 April 1940. NA-40-3 through NA-40-7 Proposed export versions, not built. Specifications (NA-40B) See also References Notes Bibliography Borth, Christy. Masters of Mass Production. Indianapolis, Indiana: Bobbs-Merrill Co., 1945. Donald, David, ed. The Complete Encyclopedia of World Aircraft. London: Orbis, 1997. . Dorr, Robert F. "North American B-25 Variant Briefing". Wings of Fame, Volume 3, 1996. London: Aerospace Publishing. . . pp. 118–141. Jones, Lloyd S. U.S. Bombers, B1-B70. Fallbrook, California: Aero Publishers, 1962. . Norton, Bill. American Bomber Aircraft Development in World War 2. Hersham, Surrey, UK: Midland Publishing, 2012. . Parker, Dana T. Building Victory: Aircraft Manufacturing in the Los Angeles Area in World War II. Cypress, California: Dana Parker Enterprises, 2013. . Reuter, Claus. Development of Aircraft Turrets in the AAF, 1917–1944. New York: S.R. Research & Publishing, 2000. . Rusinek, Ed. "A Tale of Two Dragons." North American Aviation Retirees Bulletin, Winter 2005. Yenne, Bill. The American Aircraft Factory in World War II. St. Paul, Minnesota: Zenith Press, 2006. . External links XB-21 at Aero-Web.org 1930s United States bomber aircraft NA-40 Aircraft first flown in 1939 Mid-wing aircraft Twin piston-engined tractor aircraft